Class Note for CHEM 121 at UMass(9)
Class Note for CHEM 121 at UMass(9)
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This 16 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Massachusetts taught by a professor in Fall. Since its upload, it has received 24 views.
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Date Created: 02/06/15
Mass Spectrometry Allows one to determine relative atomic and molecular masses Works by taking advantage of Newton s second law ls better called Masstocharge mz Spectrometry ls colorblind spectroscopy Accelerau39ng 0 2003 ThomsonEmokleola We can determine carbon has a mass about 12 times that of hydrogen C has 2 stable isotopes and they differ in mass 12C 120000 13C 130034 on periodic table one finds C 12011 weighted average of isotopes 12C gt 98890 13C gt 1110 H has 2 stable isotopes and they differ in mass H 10078 2H 20014 What good is this geoscientists use 160 180 ratio to determine temperature at which rocks were formed throughout history of the earth where rocks were formed extraterrestrial or not nuclear reactors require enriched uranium gt 99 of natural uranium is 238U a higher percentage of 235U is needed for efficient reactions to be effective 235U has to be enriched from 07 to gt 5 Modern Mass Spectrometers Sam le p Vacuum System Ion Mass Source Analyzer Detector We need to make qasphase ions Signal Processing and Mass spectrometers are very sensitive Readout Q Neutral molecules Ion source Q 0 0 From reservoir sampling system Repeller Eleclmn beam Ions 39 Cathode I Anode l Analyzer tube Direction of magnetic lield B Ion exit slit Electron multiplier detector Heavier ions Separated ion beam Harris Quantitative Chemical Analysis Instead of a magnetic field we can use electric fields Four rods O Quadrupole Ion Source C Detector a C O 0 53 2050cm or a slight variation to the quadrupole mass analyzer Quadrupole Ion Trap 781 kHz Wolfgang Paul and Hans Dehmelt Nobel Prize in Physics 1989 Mass Spectrometer Sam le p Vacuum System Ion Mass Source Analyzer Detector Signal Processing and Readout Recent breakthroughs in MS involve the development of new ionization techniques thermal collisional ion protein solution desolvation desolvation focusing nebulizing gas N2 Mass analyzer l Il Electrospray Ionization Courtesy of Prof Igor Kaltashov John Fenn Nobel Prize in Chemistry 2002 MatrixAssisted Laser DesorptionIonization MALDI hv Q Sample 0 Matrix Mass Analyzer Koichi Tanaka Nobel Prize in Chemistry 2002 Electrospray Ionization and MALDI are major breakthroughs because we can now make gasphase ions out of almost any molecule without destroying it including DNA and proteins human genome provides blueprint for life but proteins do the work understand cellular processes by understanding what proteins are made during certain processes how these proteins are chemically modified after being made and how much of the protein is actually made Proteomics How do we identify proteins by MS 1 We start by determining the mass of the protein 100 ionic signal au 01 O L oliiiiI 10000 20000 30000 40000 50000 mz How do we identify proteins by MS We then determine the order of some of its amino acids D o 100 g Breakdown or digest the protein g 80 into smaller pieces 3 60 lt1 I I a 40 i i E I I 20 i i I I D O l hrMLL Al I hT I 200 400 600 800 1000 1200 mz 8 100 C 8 80 Tandem Mass Spectrometry 5 mass difference between D 60 lt peaks IdentIers amIno acIds a 40 2 E 20 OJ n 0 300 400 500 rr 2600 700 800 900 How do we identify proteins by MS 3 Search protein databases and match mass and information about amino acid sequence fl mmquotmm leva am has f Eli P39V l 53139 in 1 1 lt 39 ii I an d39vm 113 J Jquot lye IHI n i 1 139 till31 quotJJ 3 E39l EE39rU a Jrqll 39jl E39mmmm39 um xl an val3 quotan 393 J IIII M AL Mann 3912 L39 Writ 39 nuuuzzrul Mquot i 1 39 39 gt In Vain 39 39 Phil1quot mm mm i J v a m runw rnn III I 39I III 39 I il l u I39Iiu lquot I f I H l 39ii quotI II I In I III 2 lnl z Iquot l u all m DI How do we identify protein modifications by MS 100 8 90 Compare unmodified and chemically g modified protein and look for mz changes E lt1 E E D D 1130 1140 1150 1160 mZ 1170 1180 1190 1200 100 90 80 i 70 60 5o 40 30 2o 10 0 Relative Abundance 1130 1140 39 39 115d 39 39 3911396039 3911397039 39 39 3911398039 39 39 3911399039 39 39 39123900
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